A nuclear electromagnetic pulse (nuclear EMP or NEMP) is a burst of
electromagnetic radiation
In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic field, electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, inf ...
created by a
nuclear explosion
A nuclear explosion is an explosion that occurs as a result of the rapid release of energy from a high-speed nuclear reaction. The driving reaction may be nuclear fission or nuclear fusion or a multi-stage cascading combination of the two, t ...
. The resulting rapidly varying
electric and
magnetic field
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...
s may couple with electrical and electronic systems to produce damaging current and
voltage surges. The specific characteristics of a particular nuclear EMP event vary according to a number of factors, the most important of which is the
altitude
Altitude or height (also sometimes known as depth) is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The exact definition and reference datum varies according to the context ...
of the detonation.
The term "electromagnetic pulse" generally excludes optical (infrared, visible, ultraviolet) and ionizing (such as X-ray and gamma radiation) ranges. In military terminology, a nuclear warhead detonated tens to hundreds of miles above the Earth's surface is known as a
high-altitude electromagnetic pulse
High-altitude nuclear explosions are the result of nuclear weapons testing within the upper layers of the Earth's atmosphere and in outer space. Several such tests were performed at high altitudes by the United States and the Soviet Union betwe ...
(HEMP) device. Effects of a HEMP device depend on factors including the altitude of the detonation,
energy yield,
gamma ray
A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...
output, interactions with the
Earth's magnetic field
Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from Earth's interior out into space, where it interacts with the solar wind, a stream of charged particles emanating from the Sun. The magnetic f ...
and
electromagnetic shielding of targets.
History
The fact that an electromagnetic pulse is produced by a nuclear explosion was known in the earliest days of nuclear weapons testing. The magnitude of the EMP and the significance of its effects were not immediately realized.
During the
first United States nuclear test on 16 July 1945, electronic equipment was shielded because
Enrico Fermi
Enrico Fermi (; 29 September 1901 – 28 November 1954) was an Italian (later naturalized American) physicist and the creator of the world's first nuclear reactor, the Chicago Pile-1. He has been called the "architect of the nuclear age" and ...
expected the electromagnetic pulse. The official technical history for that first nuclear test states, "All signal lines were completely shielded, in many cases doubly shielded. In spite of this many records were lost because of spurious pickup at the time of the explosion that paralyzed the recording equipment." During
British nuclear testing in 1952–1953, instrumentation failures were attributed to "
radioflash", which was their term for EMP.
The first openly reported observation of the unique aspects of high-altitude nuclear EMP occurred during the
helium balloon
A gas balloon is a balloon that rises and floats in the air because it is filled with a gas lighter than air (such as helium or hydrogen). When not in flight, it is tethered to prevent it from flying away and is sealed at the bottom to prevent t ...
-lofted Yucca nuclear test of the
Hardtack I series on 28 April 1958. In that test, the electric field measurements from the 1.7 kiloton weapon exceeded the range to which the test instruments were adjusted and was estimated to be about five times the limits to which the oscilloscopes were set.
The Yucca EMP was initially positive-going, whereas low-altitude bursts were negative-going pulses. Also, the
polarization of the Yucca EMP signal was horizontal, whereas low-altitude nuclear EMP was vertically polarized. In spite of these many differences, the unique EMP results were dismissed as a possible
wave propagation
Wave propagation is any of the ways in which waves travel. Single wave propagation can be calculated by 2nd order wave equation ( standing wavefield) or 1st order one-way wave equation.
With respect to the direction of the oscillation relative to ...
anomaly.
[Defense Atomic Support Agency. 23 September 1959]
"Operation Hardtack Preliminary Report. Technical Summary of Military Effects
. Report ADA369152". pp. 346–350.
The
high-altitude nuclear tests of 1962, as discussed below, confirmed the unique results of the Yucca high-altitude test and increased the awareness of high-altitude nuclear EMP beyond the original group of defense scientists. The larger scientific community became aware of the significance of the EMP problem after a three-article series on nuclear EMP was published in 1981 by
William J. Broad
William J. Broad (born March 7, 1951) is an American science journalist, author and a Senior Writer at ''The New York Times''.
Education
Broad earned a master's degree from the University of Wisconsin in 1977.[Science
Science is a systematic endeavor that builds and organizes knowledge in the form of testable explanations and predictions about the universe.
Science may be as old as the human species, and some of the earliest archeological evidence for ...]
''.
Starfish Prime
In July 1962, the US carried out the
Starfish Prime
Starfish Prime was a high-altitude nuclear test conducted by the United States, a joint effort of the Atomic Energy Commission (AEC) and the Defense Atomic Support Agency. It was launched from Johnston Atoll on July 9, 1962, and was the larges ...
test, exploding a bomb above the mid-Pacific Ocean. This demonstrated that the effects of a
high-altitude nuclear explosion
High-altitude nuclear explosions are the result of nuclear weapons testing within the upper layers of the Earth's atmosphere and in outer space. Several such tests were performed at high altitudes by the United States and the Soviet Union betwe ...
were much larger than had been previously calculated. Starfish Prime made those effects known to the public by causing electrical damage in
Hawaii
Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...
, about away from the detonation point, disabling approximately 300 streetlights, triggering numerous burglar alarms and damaging a microwave link.
Starfish Prime was the first success in the series of United States high-altitude nuclear tests in 1962 known as
Operation Fishbowl
Operation Fishbowl was a series of high-altitude nuclear tests in 1962 that were carried out by the United States as a part of the larger ''Operation Dominic'' nuclear test program. Flight-test vehicles were designed and manufactured by Avco ...
. Subsequent tests gathered more data on the high-altitude EMP phenomenon.
The
Bluegill Triple Prime
Operation Dominic was a series of 31 nuclear test explosions with a total yield conducted in 1962 by the United States in the Pacific. This test series was scheduled quickly, in order to respond in kind to the Soviet resumption of testing af ...
and
Kingfish high-altitude nuclear tests of October and November 1962 in Operation Fishbowl provided data that was clear enough to enable physicists to accurately identify the physical mechanisms behind the electromagnetic pulses.
The EMP damage of the Starfish Prime test was quickly repaired due, in part, to the fact that the EMP over Hawaii was relatively weak compared to what could be produced with a more intense pulse, and in part due to the relative ruggedness (compared to today) of Hawaii's electrical and electronic infrastructure in 1962.
The relatively small magnitude of the Starfish Prime EMP in Hawaii (about 5.6 kilovolts/metre) and the relatively small amount of damage (for example, only 1% to 3% of streetlights extinguished) led some scientists to believe, in the early days of EMP research, that the problem might not be significant. Later calculations
showed that if the Starfish Prime warhead had been detonated over the northern continental United States, the magnitude of the EMP would have been much larger (22 to 30 kV/m) because of the greater strength of the
Earth's magnetic field
Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from Earth's interior out into space, where it interacts with the solar wind, a stream of charged particles emanating from the Sun. The magnetic f ...
over the United States, as well as its different orientation at high latitudes. These calculations, combined with the accelerating reliance on EMP-sensitive microelectronics, heightened awareness that EMP could be a significant problem.
Soviet Test 184
In 1962, the
Soviet Union
The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen national ...
performed three EMP-producing nuclear tests in space over Kazakhstan, the last in the "
Soviet Project K nuclear tests
The Soviet Union's K project nuclear test series was a group of five nuclear tests conducted in 1961–1962. These tests followed the 1961 Soviet nuclear tests series and preceded the 1962 Soviet nuclear tests series.
The K project nuclear t ...
". Although these weapons were much smaller (300
kiloton) than the Starfish Prime test, they were over a populated, large landmass and at a location where the Earth's magnetic field was greater. The damage caused by the resulting EMP was reportedly much greater than in Starfish Prime. The
geomagnetic storm–like E3 pulse from Test 184 induced a current surge in a long underground
power line that caused a fire in the
power plant
A power station, also referred to as a power plant and sometimes generating station or generating plant, is an industrial facility for the generation of electric power. Power stations are generally connected to an electrical grid.
Many pow ...
in the city of
Karaganda.
After the
collapse of the Soviet Union
The dissolution of the Soviet Union, also negatively connoted as rus, Разва́л Сове́тского Сою́за, r=Razvál Sovétskogo Soyúza, ''Ruining of the Soviet Union''. was the process of internal disintegration within the Sov ...
, the level of this damage was communicated informally to US scientists. For a few years US and Russian scientists collaborated on the HEMP phenomenon. Funding was secured to enable Russian scientists to report on some of the Soviet EMP results in international scientific journals.
As a result, formal documentation of some of the EMP damage in Kazakhstan exists
but is still sparse in the
open scientific literature.
For one of the K Project tests, Soviet scientists instrumented a section of telephone line in the area that they expected to be affected by the pulse. The monitored telephone line was divided into sub-lines of in length, separated by
repeaters. Each sub-line was protected by
fuses and by
gas-filled overvoltage
When the voltage in a circuit or part of it is raised above its upper design limit, this is known as overvoltage. The conditions may be hazardous. Depending on its duration, the overvoltage event can be transient—a voltage spike—or perm ...
protectors. The EMP from the 22 October (K-3) nuclear test (also known as Test 184) blew all of the fuses and destroyed all of the overvoltage protectors in all of the sub-lines.
Published reports, including a 1998 IEEE article,
have stated that there were significant problems with ceramic insulators on overhead electrical power lines during the tests. A 2010 technical report written for
Oak Ridge National Laboratory
Oak Ridge National Laboratory (ORNL) is a U.S. multiprogram science and technology national laboratory sponsored by the U.S. Department of Energy (DOE) and administered, managed, and operated by UT–Battelle as a federally funded research and ...
stated that "Power line insulators were damaged, resulting in a short circuit on the line and some lines detaching from the poles and falling to the ground."
Characteristics
Nuclear EMP is a complex multi-pulse, usually described in terms of three components, as defined by the
International Electrotechnical Commission
The International Electrotechnical Commission (IEC; in French: ''Commission électrotechnique internationale'') is an international standards organization that prepares and publishes international standards for all electrical, electronic and r ...
(IEC).
The three components of nuclear EMP, as defined by the IEC, are called "E1", "E2" and "E3".
E1
The E1 pulse is a very fast component of nuclear EMP. E1 is a brief but intense electromagnetic field that induces high voltages in electrical conductors. E1 causes most of its damage by causing electrical
breakdown voltages to be exceeded. E1 can destroy computers and communications equipment and it changes too quickly (nanoseconds) for ordinary
surge protectors to provide effective protection from it. Fast-acting surge protectors (such as those using
TVS diodes) will block the E1 pulse.
![EMP mechanism](https://upload.wikimedia.org/wikipedia/commons/2/24/EMP_mechanism.png)
E1 is produced when
gamma radiation
A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically s ...
from the nuclear detonation
ionizes
Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule i ...
(strips electrons from) atoms in the upper atmosphere. This is known as the
Compton effect
Compton scattering, discovered by Arthur Holly Compton, is the scattering of a high frequency photon after an interaction with a charged particle, usually an electron. If it results in a decrease in energy (increase in wavelength) of the photon ...
and the resulting current is called the "Compton current". The electrons travel in a generally downward direction at
relativistic speeds (more than 90 per cent of the speed of light). In the absence of a magnetic field, this would produce a large, radial pulse of
electric current
An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The moving pa ...
propagating outward from the burst location confined to the source region (the region over which the gamma photons are attenuated). The Earth's magnetic field exerts a force on the electron flow at a right angle to both the field and the particles' original vector, which deflects the electrons and leads to
synchrotron radiation
Synchrotron radiation (also known as magnetobremsstrahlung radiation) is the electromagnetic radiation emitted when relativistic charged particles are subject to an acceleration perpendicular to their velocity (). It is produced artificially in ...
. Because the outward traveling gamma pulse is propagating at the speed of light, the synchrotron radiation of the Compton electrons adds
coherently, leading to a radiated electromagnetic signal. This interaction produces a large, brief, pulse.
[Longmire, Conrad L. LLNL-9323905, Lawrence Livermore National Laboratory. June 1986]
Justification and Verification of High-Altitude EMP Theory, Part 1
(Retrieved 2010-15-12)
Several physicists worked on the problem of identifying the mechanism of the HEMP E1 pulse. The mechanism was finally identified by
Conrad Longmire
Conrad Lee Longmire (August 23, 1921 – March 22, 2010) was an American theoretical physicist who was best known as the discoverer of the mechanism behind high-altitude electromagnetic pulse.
In 1961, Longmire was awarded the Ernest Orlando Law ...
of
Los Alamos National Laboratory
Los Alamos National Laboratory (often shortened as Los Alamos and LANL) is one of the sixteen research and development laboratories of the United States Department of Energy (DOE), located a short distance northwest of Santa Fe, New Mexico, ...
in 1963.
Longmire gives numerical values for a typical case of E1 pulse produced by a second-generation nuclear weapon such as those of
Operation Fishbowl
Operation Fishbowl was a series of high-altitude nuclear tests in 1962 that were carried out by the United States as a part of the larger ''Operation Dominic'' nuclear test program. Flight-test vehicles were designed and manufactured by Avco ...
. The typical gamma rays given off by the weapon have an energy of about 2
MeV
In physics, an electronvolt (symbol eV, also written electron-volt and electron volt) is the measure of an amount of kinetic energy gained by a single electron accelerating from rest through an Voltage, electric potential difference of one volt i ...
(
mega
Mega or MEGA may refer to:
Science
* mega-, a metric prefix denoting 106
* Mega (number), a certain very large integer in Steinhaus–Moser notation
* "mega-" a prefix meaning "large" that is used in taxonomy
* Gravity assist, for ''Moon-Earth ...
electron-volts). The gamma rays transfer about half of their energy to the ejected free electrons, giving an energy of about 1MeV.
In a vacuum and absent a magnetic field, the electrons would travel with a
current density
In electromagnetism, current density is the amount of charge per unit time that flows through a unit area of a chosen cross section. The current density vector is defined as a vector whose magnitude is the electric current per cross-sectional ar ...
of tens of
amperes
The ampere (, ; symbol: A), often shortened to amp,SI supports only the use of symbols and deprecates the use of abbreviations for units. is the unit of electric current in the International System of Units (SI). One ampere is equal to elect ...
per square metre.
Because of the downward tilt of the Earth's magnetic field at high
latitudes
In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north pol ...
, the area of peak field strength is a U-shaped region to the equatorial side of the detonation. As shown in the diagram, for nuclear detonations in the
Northern Hemisphere
The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's Nort ...
, this U-shaped region is south of the detonation point. Near the
equator
The equator is a circle of latitude, about in circumference, that divides Earth into the Northern and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles. The term can als ...
, where the Earth's magnetic field is more nearly horizontal, the E1 field strength is more nearly symmetrical around the burst location.
At geomagnetic field strengths typical of the mid-latitudes, these initial electrons spiral around the magnetic field lines with a typical radius of about . These initial electrons are stopped by collisions with air molecules at an average distance of about . This means that most of the electrons are stopped by collisions with air molecules before completing a full spiral around the field lines.
This interaction of the negatively charged electrons with the magnetic field radiates a pulse of electromagnetic energy. The pulse typically rises to its peak value in some five nanoseconds. Its magnitude typically decays by half within 200 nanoseconds. (By the IEC definition, this E1 pulse ends 1000 nanoseconds after it begins.) This process occurs simultaneously on about 10
25 electrons.
The simultaneous action of the electrons causes the resulting pulse from each electron to radiate coherently, adding to produce a single large amplitude, but narrow, radiated pulse.
Secondary collisions cause subsequent electrons to lose energy before they reach ground level. The electrons generated by these subsequent collisions have so little energy that they do not contribute significantly to the E1 pulse.
These 2 MeV gamma rays typically produce an E1 pulse near ground level at moderately high latitudes that peaks at about 50,000 volts per metre. The ionization process in the mid-
stratosphere
The stratosphere () is the second layer of the atmosphere of the Earth, located above the troposphere and below the mesosphere. The stratosphere is an atmospheric layer composed of stratified temperature layers, with the warm layers of air ...
causes this region to become an electrical conductor, a process that blocks the production of further electromagnetic signals and causes the field strength to saturate at about 50,000 volts per metre. The strength of the E1 pulse depends upon the number and intensity of the gamma rays and upon the rapidity of the gamma-ray burst. Strength is also somewhat dependent upon altitude.
There are reports of "super-EMP" nuclear weapons that are able to exceed the 50,000 volts per metre limit by unspecified mechanisms. The reality and possible construction details of these weapons are classified and are, therefore, unconfirmed in the open scientific literature
E2
The E2 component is generated by scattered gamma rays and inelastic gammas produced by
neutron
The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons beh ...
s. This E2 component is an "intermediate time" pulse that, by IEC definition, lasts from about one microsecond to one second after the explosion. E2 has many similarities to
lightning
Lightning is a naturally occurring electrostatic discharge during which two electric charge, electrically charged regions, both in the atmosphere or with one on the land, ground, temporarily neutralize themselves, causing the instantaneous ...
, although lightning-induced E2 may be considerably larger than a nuclear E2. Because of the similarities and the widespread use of lightning protection technology, E2 is generally considered to be the easiest to protect against.
According to the United States EMP Commission, the main problem with E2 is that it immediately follows E1, which may have damaged the devices that would normally protect against E2.
The EMP Commission Executive Report of 2004 states, "In general, it would not be an issue for critical infrastructure systems since they have existing protective measures for defense against occasional lightning strikes. The most significant risk is synergistic because the E2 component follows a small fraction of a second after the first component's insult, which has the ability to impair or destroy many protective and control features. The energy associated with the second component thus may be allowed to pass into and damage systems."
E3
The E3 component is different from E1 and E2. E3 is a much slower pulse, lasting tens to hundreds of seconds. It is caused by the nuclear detonation's temporary distortion of the Earth's magnetic field. The E3 component has similarities to a
geomagnetic storm. Like a geomagnetic storm, E3 can produce geomagnetically induced currents in long electrical conductors, damaging components such as power line
transformer
A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the transformer' ...
s.
Because of the similarity between solar-induced geomagnetic storms and nuclear E3, it has become common to refer to solar-induced geomagnetic storms as "Solar EMP".
"Solar EMP" does not include E1 or E2 components.
Generation
Factors that control weapon effectiveness include altitude,
yield, construction details, target distance, intervening geographical features, and local strength of the Earth's magnetic field.
Weapon altitude
According to an internet primer published by the
Federation of American Scientists
The Federation of American Scientists (FAS) is an American nonprofit global policy think tank with the stated intent of using science and scientific analysis to attempt to make the world more secure. FAS was founded in 1946 by scientists who wo ...
:
: A high-altitude nuclear detonation produces an immediate
flux
Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications to physics. For transport ph ...
of gamma rays from the nuclear reactions within the device. These
photon
A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless, so they always ...
s in turn produce high energy free electrons by Compton scattering at altitudes between (roughly) 20 and 40 km. These electrons are then trapped in the Earth's magnetic field, giving rise to an
oscillating
Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples of oscillation include a swinging pendulum ...
electric current. This current is asymmetric in general and gives rise to a rapidly rising radiated electromagnetic field called an electromagnetic pulse (EMP). Because the electrons are trapped essentially simultaneously, a very large electromagnetic source radiates
coherently.
: The pulse can easily span continent-sized areas, and this radiation can affect systems on land, sea, and air. ... A large device detonated at 400–500 km (250 to 312 miles) over
Kansas
Kansas () is a state in the Midwestern United States. Its capital is Topeka, and its largest city is Wichita. Kansas is a landlocked state bordered by Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to the ...
would affect all of the continental U.S. The signal from such an event extends to the visual horizon as seen from the burst point.
Thus, for equipment to be affected, the weapon needs to be above the
visual horizon.
The altitude indicated above is greater than that of the
International Space Station
The International Space Station (ISS) is the largest modular space station currently in low Earth orbit. It is a multinational collaborative project involving five participating space agencies: NASA (United States), Roscosmos (Russia), JAXA ...
and many
low Earth orbit
A low Earth orbit (LEO) is an orbit around Earth with a period of 128 minutes or less (making at least 11.25 orbits per day) and an eccentricity less than 0.25. Most of the artificial objects in outer space are in LEO, with an altitude never mor ...
satellites. Large weapons could have a dramatic impact on
satellite
A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioisotope ...
operations and communications such as occurred during Operation Fishbowl. The damaging effects on orbiting satellites are usually due to factors other than EMP. In the
Starfish Prime
Starfish Prime was a high-altitude nuclear test conducted by the United States, a joint effort of the Atomic Energy Commission (AEC) and the Defense Atomic Support Agency. It was launched from Johnston Atoll on July 9, 1962, and was the larges ...
nuclear test, most damage was to the satellites' solar panels while passing through radiation belts created by the explosion.
For detonations within the atmosphere, the situation is more complex. Within the range of gamma ray deposition, simple laws no longer hold as the air is
ionised
Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule ...
and there are other EMP effects, such as a radial electric field due to the separation of
Compton electrons from air molecules, together with other complex phenomena. For a surface burst, absorption of gamma rays by air would limit the range of gamma-ray deposition to approximately , while for a burst in the lower-density air at high altitudes, the range of deposition would be far greater.
Weapon yield
Typical
nuclear weapon yield
The explosive yield of a nuclear weapon is the amount of energy released when that particular nuclear weapon is detonated, usually expressed as a TNT equivalent (the standardized equivalent mass of trinitrotoluene which, if detonated, would produ ...
s used during
Cold War
The Cold War is a term commonly used to refer to a period of geopolitical tension between the United States and the Soviet Union and their respective allies, the Western Bloc and the Eastern Bloc. The term '' cold war'' is used because the ...
planning for EMP attacks were in the range of . This is roughly 50 to 500 times the size of the Hiroshima and Nagasaki bombs. Physicists have testified at United States Congressional hearings that weapons with yields of or less can produce a large EMP.
The EMP at a fixed distance from an explosion increases at most as the square root of the yield (see the illustration to the right). This means that although a weapon has only of the energy release of the Starfish Prime test, the EMP will be at least as powerful. Since the E1 component of nuclear EMP depends on the prompt gamma-ray output, which was only 0.1% of yield in Starfish Prime but can be of yield in low-yield pure
nuclear fission
Nuclear fission is a reaction in which the nucleus of an atom splits into two or more smaller nuclei. The fission process often produces gamma photons, and releases a very large amount of energy even by the energetic standards of radio ...
weapons, a bomb can easily be as powerful as the Starfish Prime at producing EMP.
The total prompt gamma-ray energy in a fission explosion is of the yield, but in a detonation the triggering explosive around the bomb core absorbs about of the prompt gamma rays, so the output is only about of the yield. In the
thermonuclear
Thermonuclear fusion is the process of atomic nuclei combining or “fusing” using high temperatures to drive them close enough together for this to become possible. There are two forms of thermonuclear fusion: ''uncontrolled'', in which the re ...
Starfish Prime the fission yield was less than 100% and the thicker outer casing absorbed about 95% of the prompt gamma rays from the pusher around the fusion stage.
Thermonuclear weapons
A thermonuclear weapon, fusion weapon or hydrogen bomb (H bomb) is a second-generation nuclear weapon design. Its greater sophistication affords it vastly greater destructive power than first-generation nuclear bombs, a more compact size, a lowe ...
are also less efficient at producing EMP because the first stage can
pre-ionize the air
which becomes conductive and hence rapidly shorts out the
Compton currents generated by the
fusion stage. Hence, small pure fission weapons with thin cases are far more efficient at causing EMP than most megaton bombs.
This analysis, however, only applies to the fast E1 and E2 components of nuclear EMP. The
geomagnetic storm-like E3 component of nuclear EMP is more closely proportional to the total energy yield of the weapon.
Target distance
In nuclear EMP all of the components of the electromagnetic pulse are generated outside of the weapon.
For
high-altitude nuclear explosion
High-altitude nuclear explosions are the result of nuclear weapons testing within the upper layers of the Earth's atmosphere and in outer space. Several such tests were performed at high altitudes by the United States and the Soviet Union betwe ...
s, much of the EMP is generated far from the detonation (where the gamma radiation from the explosion hits the upper atmosphere). This electric field from the EMP is remarkably uniform over the large area affected.
According to the standard reference text on nuclear weapons effects published by the U.S. Department of Defense, "The peak electric field (and its amplitude) at the Earth's surface from a high-altitude burst will depend upon the explosion yield, the height of the burst, the location of the observer, and the orientation with respect to the
geomagnetic field
Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from Earth's interior out into space, where it interacts with the solar wind, a stream of charged particles emanating from the Sun. The magnetic fi ...
. As a general rule, however, the field strength may be expected to be tens of kilovolts per metre over most of the area receiving the EMP radiation."
The text also states that, "...over most of the area affected by the EMP the electric field strength on the ground would exceed 0.5''E''
max. For yields of less than a few hundred kilotons, this would not necessarily be true because the field strength at the Earth's tangent could be substantially less than 0.5''E''
max."
(''E''
max refers to the maximum electric field strength in the affected area.)
In other words, the electric field strength in the entire area that is affected by the EMP will be fairly uniform for weapons with a large gamma-ray output. For smaller weapons, the electric field may fall at a faster rate as distance increases.
Super-EMP
Also known as an "Enhanced-EMP", a super-electromagnetic pulse is a relatively new type of warfare in which a
nuclear weapon
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission bomb) or a combination of fission and fusion reactions ( thermonuclear bomb), producing a nuclear explosion. Both bom ...
is designed to create a far greater
electromagnetic pulse
An electromagnetic pulse (EMP), also a transient electromagnetic disturbance (TED), is a brief burst of electromagnetic energy. Depending upon the source, the origin of an EMP can be natural or artificial, and can occur as an electromagnetic fie ...
in comparison to standard nuclear
weapons of mass destruction
A weapon of mass destruction (WMD) is a chemical, biological, radiological, nuclear, or any other weapon that can kill and bring significant harm to numerous individuals or cause great damage to artificial structures (e.g., buildings), natura ...
. These weapons capitalize on the E1 pulse component of a detonation involving
gamma ray
A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...
s, creating an EMP yield of potentially up to 200,000 volts per meter.
For decades, numerous countries have experimented with the creation of such weapons, most notably
China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
and
Russia
Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...
.
China
According to a statement made in writing by the Chinese military, the country has super-EMPs and has discussed their use in attacking
Taiwan
Taiwan, officially the Republic of China (ROC), is a country in East Asia, at the junction of the East and South China Seas in the northwestern Pacific Ocean, with the People's Republic of China (PRC) to the northwest, Japan to the nort ...
. Such an attack would debilitate information systems in the nation, allowing China to move in and attack it directly using soldiers. The Taiwanese military has subsequently confirmed Chinese possession of super-EMPs and their possible destruction to
power grids
An electrical grid is an interconnected network for electricity delivery from producers to consumers. Electrical grids vary in size and can cover whole countries or continents. It consists of:Kaplan, S. M. (2009). Smart Grid. Electrical Power ...
.
In addition to Taiwan, the possible implications of attacking the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
with these weapons was examined by China. While the United States also possess nuclear weapons, the country has not experimented with super-EMPs and is hypothetically highly vulnerable to any future attacks by nations. This is due to the country's reliance on computers to control much of the government and economy.
Abroad, U.S. aircraft carriers stationed within a reasonable range of an exploding bomb could potentially be subject to complete destruction of missiles on board, as well as
telecommunication systems
A communications system or communication system is a collection of individual telecommunications networks, transmission systems, relay stations, tributary stations, and terminal equipment usually capable of interconnection and interoperatio ...
that would allow them to communicate with nearby vessels and controllers on land.
Russia
Since the Cold War, Russia has experimented with the design and effects of EMP bombs. More recently, the country has performed several
cyberattack
A cyberattack is any offensive maneuver that targets computer information systems, computer networks, infrastructures, or personal computer devices. An attacker is a person or process that attempts to access data, functions, or other restricted ...
s on the United States, which some analysts believe suggests possible future nationwide blackouts caused by super-EMPs, since Russia is known to possess them. Along with ordinary warheads equipped with Super-EMP capabilities, Russia has been developing
hypersonic
In aerodynamics, a hypersonic speed is one that exceeds 5 times the speed of sound, often stated as starting at speeds of Mach 5 and above.
The precise Mach number at which a craft can be said to be flying at hypersonic speed varies, since in ...
missiles that, in 2021, are far more difficult for U.S. defenses in the form of radars and satellites to detect in a timely manner. This method makes the act of
nuclear deterrence
Deterrence theory refers to the scholarship and practice of how threats or limited force by one party can convince another party to refrain from initiating some other course of action. The topic gained increased prominence as a military strategy ...
, which is a key strategy for the United States in preventing
nuclear war
Nuclear warfare, also known as atomic warfare, is a theoretical military conflict or prepared political strategy that deploys nuclear weaponry. Nuclear weapons are weapons of mass destruction; in contrast to conventional warfare, nuclear w ...
, nearly impossible.
Plans of a device that is capable of placing a nuclear weapon into space were first introduced by the
Soviet Union
The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen national ...
in 1962 when they developed a system, known as
Fractional Orbital Bombardment System, to deliver nuclear weapons from above the
Earth's atmosphere
The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing for ...
.
Compared to super-EMPs that target ground operations, proposals have been made by Russia to develop
satellite
A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioisotope ...
s supplied with similar EMP capabilities. This would call for detonations up to above the Earth's surface, with the potential to disrupt the electronic systems of U.S. satellites suspended in orbit around the planet, many of which are vital for deterrence and alerting the country of possible incoming missiles.
Effects
An energetic EMP can temporarily upset or permanently damage electronic equipment by generating high voltage and high current surges; semiconductor components are particularly at risk. The effects of damage can range from imperceptible to the eye, to devices literally blowing apart. Cables, even if short, can act as antennas to transmit pulse energy to the equipment.
Vacuum tube vs. solid state electronics
Older,
vacuum tube
A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric voltage, potential difference has been applied.
The type kn ...
(valve)-based equipment is generally much less vulnerable to nuclear EMP than
solid state equipment, which is much more susceptible to damage by large, brief voltage and current surges.
Soviet
The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, ...
Cold War
The Cold War is a term commonly used to refer to a period of geopolitical tension between the United States and the Soviet Union and their respective allies, the Western Bloc and the Eastern Bloc. The term '' cold war'' is used because the ...
-era military aircraft often had
avionics
Avionics (a blend word, blend of ''aviation'' and ''electronics'') are the Electronics, electronic systems used on aircraft. Avionic systems include communications, Air navigation, navigation, the display and management of multiple systems, ...
based on vacuum tubes because solid-state capabilities were limited and vacuum-tube gear was believed to be more likely to survive.
Other components in vacuum tube circuitry can be damaged by EMP. Vacuum tube equipment was damaged in the 1962 testing.
The solid state
PRC-77 VHF
Very high frequency (VHF) is the ITU designation for the range of radio frequency electromagnetic waves (radio waves) from 30 to 300 megahertz (MHz), with corresponding wavelengths of ten meters to one meter.
Frequencies immediately below VHF ...
manpackable two-way radio survived extensive EMP testing.
[Seregelyi, J.S, et al]
Report ADA266412 "EMP Hardening Investigation of the PRC-77 Radio Set
" Retrieved 2009-25-11 The earlier PRC-25, nearly identical except for a vacuum tube final amplification stage, was tested in EMP simulators, but was not certified to remain fully functional.
Electronics in operation vs. inactive
Equipment that is running at the time of an EMP is more vulnerable. Even a low-energy pulse has access to the power source, and all parts of the system are illuminated by the pulse. For example, a high-current arcing path may be created across the power supply, burning out some device along that path. Such effects are hard to predict and require testing to assess potential vulnerabilities.
[
]
On aircraft
Many nuclear detonations have taken place using
aerial bomb
An aerial bomb is a type of explosive or incendiary weapon intended to travel through the air on a predictable trajectory. Engineers usually develop such bombs to be dropped from an aircraft.
The use of aerial bombs is termed aerial bombing.
...
s. The
B-29
The Boeing B-29 Superfortress is an American four-engined propeller-driven heavy bomber, designed by Boeing and flown primarily by the United States during World War II and the Korean War. Named in allusion to its predecessor, the B-17 Fly ...
aircraft that delivered the nuclear weapons at
Hiroshima
is the capital of Hiroshima Prefecture in Japan. , the city had an estimated population of 1,199,391. The gross domestic product (GDP) in Greater Hiroshima, Hiroshima Urban Employment Area, was US$61.3 billion as of 2010. Kazumi Matsui h ...
and
Nagasaki
is the capital and the largest city of Nagasaki Prefecture on the island of Kyushu in Japan.
It became the sole port used for trade with the Portuguese and Dutch during the 16th through 19th centuries. The Hidden Christian Sites in the ...
did not lose power from electrical damage, because
electron
The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family,
and are generally thought to be elementary particles because they have no kn ...
s (ejected from the air by gamma rays) are stopped quickly in normal air for bursts below roughly , so they are not significantly deflected by the Earth's magnetic field.
If the aircraft carrying the
Hiroshima
is the capital of Hiroshima Prefecture in Japan. , the city had an estimated population of 1,199,391. The gross domestic product (GDP) in Greater Hiroshima, Hiroshima Urban Employment Area, was US$61.3 billion as of 2010. Kazumi Matsui h ...
and
Nagasaki
is the capital and the largest city of Nagasaki Prefecture on the island of Kyushu in Japan.
It became the sole port used for trade with the Portuguese and Dutch during the 16th through 19th centuries. The Hidden Christian Sites in the ...
bombs had been within the intense nuclear radiation zone when the bombs exploded over those cities, then they would have suffered effects from the
charge separation
Charge or charged may refer to:
Arts, entertainment, and media Films
* ''Charge, Zero Emissions/Maximum Speed'', a 2011 documentary
Music
* ''Charge'' (David Ford album)
* ''Charge'' (Machel Montano album)
* ''Charge!!'', an album by The Aqua ...
(radial) EMP. But this only occurs within the severe blast radius for detonations below about altitude.
During
Operation Fishbowl
Operation Fishbowl was a series of high-altitude nuclear tests in 1962 that were carried out by the United States as a part of the larger ''Operation Dominic'' nuclear test program. Flight-test vehicles were designed and manufactured by Avco ...
, EMP disruptions were suffered aboard a
KC-135
The Boeing KC-135 Stratotanker is an American military aerial refueling aircraft that was developed from the Boeing 367-80 prototype, alongside the Boeing 707 airliner. It is the predominant variant of the C-135 Stratolifter family of transpo ...
photographic aircraft flying from the detonations at burst altitudes.
The vital electronics were less sophisticated than today's and the aircraft was able to land safely.
Modern aircraft are heavily reliant on solid state electronics which are very susceptible to EMP blasts. Therefore, airline authorities are creating high intensity radiated fields (HIRF) requirements for new air planes to help prevent the chance of crashes caused by EMPs or electromagnetic interference (EMI). To do this all parts of the airplane must be conductive. This is the main shield from EMP blasts as long as there are no holes for the waves to penetrate into the interior of the airplane. Also, by insulating some of the main computers inside the plane also add an extra layer of protection from EMP blasts.
On cars
An EMP would probably not affect most cars, despite modern cars' heavy use of electronics, because cars' electronic circuits and cabling are likely too short to be affected. In addition, cars' metallic frames provide some protection. However, even a small percentage of cars breaking down due to an electronic malfunction would cause temporary traffic jams.
On small electronics
An EMP has a smaller effect the shorter the length of an electrical conductor; though other factors affect the vulnerability of electronics as well, so no cutoff length determines whether some piece of equipment will survive. However, small electronic devices, such as wristwatches and cell phones, would most likely withstand an EMP.
This is true only if they are not plugged into or in operation. Electronics plugged into the grid could see a massive surge and end up sustaining permanent damage to the devices similarly, if there was a lightning strike. EMPs could also blow all the breakers in a home and damage devices not connected to a surge protector. Or if the house has a proper whole house surge protector that can negate the effects of an EMP attack, and other protective devices that will protect the house.
On humans and animals
Though electric potential difference can accumulate in electrical conductors after an EMP, it will generally not flow out into human or animal bodies, and thus contact is safe.
EMPs of sufficient magnitude and length have the potential to affect the human body. Possible side effects include cellular mutations, nervous system damages, internal burns, brain damage, and temporary problems with thinking and memory. However, this would be in extreme cases like being near the center of the blast and being exposed to a large amount of radiation and EMP waves.
A study found that exposure to 200–400 pulses of EMP caused the leaking of vessels in the brain, leakage that has been linked to small problems with thinking and memory recollection. These effects could last up to 12 hours after the exposure. Due to the long exposure time needed to see any of these effects it is unlikely that anyone would see these effects even if exposed for a small period of time. Also, the human body will see little effect as signals are passed chemically and not electrically making it hard to be affected by EMP waves.
Post–Cold War attack scenarios
The United States EMP Commission was created by the
United States Congress
The United States Congress is the legislature of the federal government of the United States. It is bicameral, composed of a lower body, the House of Representatives, and an upper body, the Senate. It meets in the U.S. Capitol in Washing ...
in 2001. The commission is formally known as the Commission to Assess the Threat to the United States from Electromagnetic Pulse (EMP) Attack.
The Commission brought together notable scientists and technologists to compile several reports. In 2008, the Commission released the "Critical National Infrastructures Report".
This report describes the likely consequences of a nuclear EMP on civilian infrastructure. Although this report covered the United States, most of the information is applicable to other industrialized countries. The 2008 report was a follow-up to a more generalized report issued by the commission in 2004.
In written testimony delivered to the United States Senate in 2005, an EMP Commission staff member reported:
The United States EMP Commission determined that long-known protections are almost completely absent in the civilian infrastructure of the United States and that large parts of US military services were less-protected against EMP than during the Cold War. In public statements, the Commission recommended making electronic equipment and electrical components resistant to EMP – and maintaining spare parts inventories that would enable prompt repairs.
The United States EMP Commission did not look at other nations.
In 2011, the
Defense Science Board
The Defense Science Board (DSB) is a committee of civilian experts appointed to advise the U.S. Department of Defense on scientific and technical matters. It was established in 1956 on the recommendation of the second Hoover Commission.
Charter
...
published a report about the ongoing efforts to defend critical military and civilian systems against EMP and other nuclear weapons effects.
The United States military services developed, and in some cases published, hypothetical EMP attack scenarios.
In 2016, the Los Alamos Laboratory started phase 0 of a multi-year study (through to phase 3) to investigate EMPs which prepared the strategy to be followed for the rest of the study.
In 2017, the US Department of Energy published the "DOE Electromagnetic Pulse Resilience Action Plan",
[DOE and partners]
DOE Electromagnetic Pulse Resilience Action Plan
DOE, January 2017 Edwin Boston published a dissertation on the topic and the EMP Commission published "Assessing the threat from electromagnetic pulse (EMP)". The EMP commission was closed in summer 2017. They found that earlier reports had underestimated the effects of an EMP attack on the national infrastructure, highlighted issues with communications from the DoD due to the classified nature of the material, and recommended that the DHS instead of going to the DOE for guidance and direction should directly cooperate with the more knowledgeable parts of the DOE. Several reports are in process of being released to the general public.
Protecting infrastructure
The problem of protecting civilian infrastructure from electromagnetic pulse has been intensively studied throughout the European Union, and in particular by the United Kingdom.
As of 2017, several
power utility companies in the United States had been involved in a three-year research program on the impact of HEMP to the United States power grid led by an industry non-profit organization,
Electric Power Research Institute
EPRI, is an American independent, nonprofit organization that conducts research and development related to the generation, delivery, and use of electricity to help address challenges in the energy industry, including reliability, efficiency, affor ...
(EPRI).
In 2018, the US Department of Homeland Security released the Strategy for Protecting and Preparing the Homeland against Threats from Electromagnetic Pulse (EMP) and Geomagnetic Disturbance (GMD), which was the Department’s first articulation of a holistic, long-term, partnership-based approach to protecting critical infrastructure and preparing to respond and recover from potentially catastrophic electromagnetic incidents. Progress on that front is described in the EMP Program Status Report.
NuScale, the small modular nuclear reactor company from Oregon, US, has made their reactor resistant to EMP.
In fiction and popular culture
By 1981, a number of articles on nuclear electromagnetic pulse in the
popular press spread knowledge of the nuclear EMP phenomenon into the
popular culture
Popular culture (also called mass culture or pop culture) is generally recognized by members of a society as a set of practices, beliefs, artistic output (also known as, popular art or mass art) and objects that are dominant or prevalent in a ...
. EMP has been subsequently used in a wide variety of fiction and other aspects of popular culture.
The popular media often depict EMP effects incorrectly, causing misunderstandings among the public and even professionals, and official efforts have been made in the United States to set the record straight.
The
United States Space Command commissioned science educator
Bill Nye
William Sanford Nye (born November 27, 1955), popularly known as Bill Nye the Science Guy, is an American mechanical engineer, science communicator, and television presenter. He is best known as the host of the science television show ''Bill ...
to narrate and produce a video called "Hollywood vs. EMP" so that inaccurate Hollywood fiction would not confuse those who must deal with real EMP events.
[Air Force Space Command]
''Hollywood vs. EMP''
Manitou Motion Picture Company, 2009 (not available to the general public). The video is not available to the general public.
See also
References
Citations
Sources
*
*
*
*
Further reading
* A 21st Century Complete Guide to Electromagnetic Pulse (EMP) Attack Threats, Report of the Commission to Assess the Threat to the United States from Electromagnetic ... High-Altitude Nuclear Weapon EMP Attacks (CD-ROM),
* Threat posed by electromagnetic pulse (EMP) to U.S. military systems and civil infrastructure: Hearing before the Military Research and Development Subcommittee – first session, hearing held July 16, 1997,
* Electromagnetic Pulse Radiation and Protective Techniques,
External links
*
ttps://web.archive.org/web/19961213134039/http://www.usace.army.mil/inet/usace-docs/eng-pamphlets/ep.htm Electromagnetic Pulse (EMP) and Tempest Protection for Facilities–
U.S. Army Corps of Engineers
, colors =
, anniversaries = 16 June (Organization Day)
, battles =
, battles_label = Wars
, website =
, commander1 = ...
EMP data from ''Starfish'' nuclear test measured by Richard Wakefield of LANL, and review of evidence pertaining to the effects 1,300 km away in Hawaii, also review of Russian EMP tests of 1962Read Congressional Research Service (CRS) Reports regarding HEMPMIL-STD-188-125-1Commission to Assess the Threat to the United States from Electromagnetic Pulse (EMP) AttackU.S. Presidential Executive Order concerning EMPProtecting Electrical Equipment: good practice for preventing high altitude electromagnetic pulse impacts, De Gruyter, 2019
{{DEFAULTSORT:Electromagnetic Pulse
Electromagnetic radiation
Energy weapons
Nuclear weapons
Electromagnetic compatibility
Bombs
Electronic warfare
Pulsed power